The present invention relates to laser texturing of magnetic data storage media and more particularly to processes for controlling the shapes and orientations of texturing features formed in such texturing processes, as well as the resulting storage media.
Laser texturing of magnetic disks, particularly over areas designated for contact with data transducing heads, is known to reduce friction and improve wear characteristics as compared to mechanically textured disks. Texturing involves focusing a laser beam onto a disk substrate surface at multiple locations, forming at each location a depression surrounded by a raised rim, as in U.S. Pat. No. 5,062,021 (Ranjan) and U.S. Pat. No. 5,108,781 (Ranjan). Alternatively, as shown in International Publication No. WO 97/07931 published Mar. 6, 1977 (Meyer), the laser beam also can be used to form a bump or nodule at each of the multiple locations. In some cases, a dome or bump is surrounded by a ring.
In any event, the individual topographical features are circular or axisymmetric, more particularly symmetrical about a vertical central axis in the case of features formed on a horizontal surface. While textures based on these features exhibit considerable improvement over mechanically formed textures, the ongoing quest for lower transducing head flying heights and shorter times for accessing data lead to more stringent tribological requirements.
Meeting these requirements has been difficult in view of certain structural characteristics of the circular, axisymmetric rims and nodules. These features include a relatively small radius of curvature, a relatively large nodule height as compared to diameter, and large rim height compared to rim width. The resulting abrupt changes in surface elevation cause turbulence at the head/media interface. This results in undesirably high levels of acoustic energy at take-off and landing of the transducing head, i.e. at disk accelerations and decelerations. The closed, rim-like features have exhibited a tendency to collect debris, and their radial component can generate a drag force thought to contribute to dynamic friction.
Therefore, it is an object of the present invention to provide magnetic data storage media with transducer contact regions textured for improved wear and reduced dynamic friction.
Another object is to provide a process for using a laser to texture the surfaces of magnetic data storage media, with more control over the shape and orientation and texturing features formed by the laser to impart a desired roughness.
A further object is to provide a laser texturing process that affords more consistency in forming asymmetrical features such as rims and nodules on textured magnetic media.
Yet another object is to provide magnetic media in which the orientation of non-circular, non-axisymmetric topographical features is determined with reference to the direction of transducing head accelerations and decelerations, to increase the performance benefits derived from the asymmetries.